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Is flying without sunglasses in daylight doable in a Cessna 172?
Do the windows in a 172 provide any protection from the sun or is too bright? Particularly, if one wants to do a flying lesson and was told to bring sunglasses more than once.  So, is it critical?  My friend doesn't have sunglasses and would have to get prescribed ones which he can't get now. He got a gift of a flying lesson so he wants to try it but is being in the plane without sunglasses doable?  Or will he be squinting the entire time? Or is it really bad for your eyes?

In broad daylight (where the sun is high), definitely doable. I have no problem looking out at all. Sunrise or sunset, better get them.

@kevin  If the sun sets around 4pm what block of time is the absolute best without sunglasses?

It isn't block of time, it's the heading. You don't want to be landing at runway 27 without sunglasses...

@kevin  Clueless here. Haha!  Apparently it's at an airport in downtown Toronto, Canada.  Does that info help? What's special about 27?

@verve - landing on runway 27 near sunset would have you looking at the setting sun. Also there are quite a few airports in the greater Toronto area ;)

@verve Runways are numbered based on their heading. Runway 27 means that the heading is around 270 degrees, which is West, where the sun sets, which is why he said that wouldn't be fun in the late afternoon.

"downtown" Toronto is likely to mean the Toronto Island Airport

Not currently having prescription sunglasses is understandable, but there are two important things to consider. First - the cost of prescription sunglasses is eclipsed by just a few flight lessons, so even if the current lessons are a gift, that gift will eventually run out. Second, clip-on sunglasses (they clip over regular prescription glasses) are very inexpensive.

I always bring the sunnies and make the decision whether to wear or not wear them after doing the walk around inspection. By then I've usually got a good idea if it's bright enough to need them or not. Mostly, summer + daytime + no or little cloud, or flying around dawn or dusk = need them. Otherwise, just stick them somewhere handy. It's a bit cramped in the cockpit, so I always keep them on my person (assume I can't get to anything in my flight bag). Better to have them and take them off then need them and can't get to them.

Definitely doable. No real protection from the sun just through the windshield but I flew a C172 for many years only using sunglasses occasionally. Just don't make the same mistake I did when I first started flying- paid a lot for a pair of polarised sunglasses then jumped in the cockpit and all the LCD screens went blank! :)

What kind of sunglasses is right for flying?

The ones that make you look real cool

@verve it's true! Some that make you look cool. Haha. No but some that almost 'wrap-around' can be good. Otherwise, the contrast between the brightness seen out of the corner of your eyes, and the darkness through the sunglasses can make seeing inside the cockpit quite difficult

I don't like wrap around because they inhibit my peripheral vision.

@verve The cheapest ones that work for you. Preferably non-polarized (for the reasons mentioned above).

Big +1 for mentioning the problem with polarized glasses and LCD screens.  (it goes for certain iPads and other cockpit accessories as well).  Last time I went to buy sunglasses, I asked for non-polarized, and the salesman immediately responded with, "Are you a pilot?". :)

Using polarized glasses depends on the screens your looking at.  If your using round-dial, or G1000 there should be no problem at all.  The problem arises when viewing a polarized screen with polarized glasses.  If you are using a consumer tablet that has a polarized screen, then you'll run into trouble.

@SpongeBob: ALL LCD screens are polarized by principle. There is no way to make an LCD that is not polarized (and G1000 has LCD, so polarized displays). Then it depends on the plane of polarization. Polarized sunglasses are always horizontally polarized. If the display is also horizontally polarized, it is actually visible better than without the glasses. But if it is polarized vertically, it is completely invisible.

All this info is super-useful! There like a zillion sunglass lenses type.  Wonder which colour lens is better?

There are two main issues here: brightness, and UV protection. For brightness, it's really no different from being in a car. If the weather is cloudy or just not very bright then you won't need sunglasses in order to see. But if the sun is very bright, if you're flying over water or snow, or into the setting sun etc. then you would need them to see in exactly the same way that you would need them in a car (or on a boat) in similar conditions.
The UV question depends on the aircraft. Light aircraft windows are not made of glass and don't offer the same kind of UV protection that most car windows do. But they still do protect against UV and the bigger concern is apparently with glass windows found in larger aircraft that also fly higher where UV is more intense:

[...] glass laminate windscreens allowed higher levels of potentially
  damaging UV-A radiation to be transmitted than did plastic.
  Professional pilots who routinely fly at higher altitude for longer
  periods of time than private pilots should take special precautions to
  protect their eyes from UV exposure.

In any case, for one flight it won't matter at all, but if your friend continues to fly then he should really get a pair of sunglasses with UV protection. The FAA has a detailed pilot's guide to sunglasses here.
And as someone has already mentioned, polarized glasses are not recommended in aircraft because they prevent you seeing LCD screens clearly.

The acrylic in light aircraft windows actually offers pretty good UV protection (cuts off most UV below ~300 nanometers, similar to "regular" glass) -- this is why photochromic eyeglass lenses (Transitions & similar) won't darken much in the cockpit. (The acrylic absorbing UV light is one of the factors that causes yellowing, haze, and crazing on the windows of aircraft that spend their life on a ramp.)

@voretaq7 Interesting, I have to admit that I was basing that on some second-hand knowledge but an FAA study on this does say that glass (especially at altitude) lets more UV through than GA aircraft. I'll update my answer.

@Pondlife : The discussion about UV made me wonder: do you get sunburnt through this kind of window?

Sunglasses are not absolutely necessary when flying. I have flown the Cessna 172 with regular glasses only, and encountered no difficulty looking outside and inside.
If the area is covered with snow, it is better to wear glasses to protect the eyes though.
If you're flying during sunrise or sunset, better get them. On the Cessna 172, there is a shield (similar to that in cars) that can be unfolded from above if you encounter strong sunlight:
Although, some times even the pros can't bear it:

Mmm, always thought those were inner leading edge slats ;)

@kevin  Like a car shield?!!! Interesting, would have never thought a plane had that.  Do most small planes have that?

Do the newer models of the 172 have the shield?

@verve I haven't flown a lot of various models to tell. But it's a common thing, unless the cockpit has a glass canopy (like those in fighter jets).

Funny how that 172's registration is, in part, 172. I wonder if someone was bored at work that day?

Nobody needs sunglasses, they are a just a convenience. They are very helpful for sure, especially in bright sunlight and hazy conditions, but not absolutely essential.
As for what to get you want non-polarized, and if you have require an eyeglass prescription on your medical the sunglasses will need to be that prescription.

why non-polarized? I fly with polarized without problems.

ah, I see it can cause problems with some glass cockpits. depends on the angle of polarization of the glasses and the screens. I haven’t had problems with G1000 in C172SP.

No you don't "need" them but I would strongly advise them for a few reasons,
UV Protection
Not only do the front windshields of GA planes provide little UV protection you are flying at altitude and the higher you go the less natural UV protection you will get. Granted the change may me minimal it is still present.
Comfort
Long exposure to bright sunlight can cause the eyes to tire out which can make it harder to see. You can actually get sun burn on your retina if you are exposed directly for to long. The last thing you want to happen when you are flying is to impair your vision in any way or simply get fatigued. That is when you start to make mistakes in a plane.
Looks
Who doesn't look great in aviators...
Some Advice
I also wear glasses regularly for distance (like your friend). When I started flying it was actually cheaper (or about even) to get fit for contacts and buy a nice pair of aviators than it was to get prescription sunglasses cut. I now don't have to worry about my sun glass prescription having to be cut or losing a very expensive pair of prescription sunglasses.
As mentioned I would NOT get polarized sun glasses because of the issues with glass cockpits. I have a pair of Ray-Ban aviators with the G15 (non polarized) glass and they are great. That being said I would also opt for more function over style here. Don't get half fade lenses or any of that stuff either it may look cooler but it wont provide any sun protection on the bottom half of the lens. You want something that provides good protection but still allows a good amount of light in as you will still have to read the instruments.
Edit
G15 is the traditional green glass that Ray-Ban uses in their sunglasses. It provides good protection with out the need for polarization. I suggested it because I also had a pair of the half fade Ray-Bans that I tried to fly with when I first started and they were terrible. They simply did not block enough light to be as effective as I wanted/needed them to be. The G15 provides a good amount of coverage with out using polarization and thus without interfering with glass cockpits if you happen to end up in that kind of plane.
I do not know how long you need to be exposed to get permanent eye damage but I tend to not play around with these kinds of issues, especially if it will permanently hamper my ability to fly. A decent pair of sun glasses be it Ray-Bans or any other of the popular brands may run you $100-$150 which pales in comparison to what you will spend getting your PPL.

What exactly is g-15?

Retina burns?  Oof!  How long does the exposure have to be?

I will edit my answer to reflect these questions.

Oh, so G15 is a Ray Ban thing?  What is the common term in other brands?

It is, I don't know of the common term is for it but any decent lenses will do as long as they are not polarized. When it comes to nice sunglasses for what its worth Ray Bans are not as expensive as some of their competitors.

It is just like driving out in the open, like on a desert highway. If you would not mind driving for an hour and a half on a desert highway in the midday summer sun, then you will have no problem during your lesson.

It never hurts to bring your sunglasses along. Before getting in the plane, you'll do a visual inspection of the aircraft on the ground by walking around it and looking at things like flaps, ailerons, lights, etc. This usually happens on the ramp which is out in the open so it's an excellent time to gauge whether to wear your sunnies for the flight or not. At least, that's what I do.
It isn't that different from driving a car (or even better - riding a motorbike) out in open countryside, it depends mostly on the brightness of the day, the season, and how low the sun is in the sky. Not all planes have sun visors, so you'll definitely want your sunnies if the sun is low in the sky.
If you plan to do a lot of flying
AS/NZS 1067:2003 requires all sunglasses to meet minimum standards for glare, UV protection and colouration. All sunglasses sold are required to meet the standard. If you're in another country and plan to do a lot of flying, you'll want to check what laws apply to sunglasses (if any) and what UV and glare protection is provided by the glasses you intend to use.
The hazards associated with repeat, high-UV sun exposure to the eyes include inflammation, cataracts, eyelid cancer, retina degeneration and impaired night vision, so it's well worth protecting your vision with good quality UV blocking sunglasses.
Enjoy your flight!


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What frequencies can you freely speak on?
Are there any frequencies that you can use to communicate with your family at home when you are flying and for a wokie talkie I am wondering if there are just any frequencies that you can speak freely on to people on the ground please may someone help.
By the way I'm a halecopter pilot.

You can always get a Amateur Radio License, commonly referred to as HAM radio. There are quite a few private pilots who are HAM radio operators that take radios with them when flying.
There are even a few commercial pilots with HAM licenses that make contact while flying.

The operator of the ground station must also have an amateur license.

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Structure that holds the twin-engine on an aircraft
What is the name of that big structure (in red) that holds the engine?

In English (and probably generally) "nacelle" is, basically, the word you're after

The external part is called "engine nacelle". Internally there's the "engine nacelle structure"... and the engine itself obviously.
This is how it looks like for example in a Beechcraft Starship (cutaway source):

I am not sure that piston aircraft, as shown in the question, have "nacelles".  Generally, that term is used for gas turbine engines, such as the Starship, shown in this answer.  But, the question showed a piston as an example.

Mmh, cowling seems to be a more generic term used also for cars and bikes. But I'm not a native English speaker so I can't tell for sure the differences between the two terms

The item shown in red does not support or contain that engine.  It is just an outer skin that can be removed for doing maintenance.

@Adam: This might actually be a good question for http://english.stackexchange.com/ As far as I understand it, cowling is the removable part while nacelle is the whole assembly.

Nacelle is the correct term for any pod like engine enclosure such as this. A cowling just covers the engine and is usually used when an engine is faired into another structure like the fuselage. I'm not sure "engine nacelle structure" is a thing. A prop engine is usually held in place by an engine mount, a turbofan engine is held in place by a pylon.

What you have circled is the engine cowling.  That doesn't hold the engine onto the wing, but instead is for aerodynamic purposes.  The engine is connected to the wing with engine mounts that are not visible but would look something like this:  Cessna 172 engine mount (although this example is for a different aircraft type)

The cowling is merely the skin of the nacelle. For engines mounted on the nose, there is no nacelle, but still a cowling.

It depends on what you're asking for. The external structure structure you highlighted is the engine fairing. The Piper P-39 engines are mounted in engine bays:

P-39 engine bay, source: Flickr, by Errol Cavit.
On larger aircraft, each engine is fixed to a strut using engine mounts and thrust links. The strut is protected by a pylon fairing and part of the wing structure:

CFM56 and pylon, source.
The engine fairing, called a nacelle, contains more than the engine, e.g. the thrust reverser mechanism, separate from the engine and provided by the nacelle manufacturer, and the fan flow duct.

More:
How is a turboprop engine mounted to the wing?
How are engines mounted onto wings?
What are different components of an engine pylon?

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Is using trim helpful on the final when landing?
I remember my old instructor used trim during traffic pattern. I believe it is pretty common on the downwind but he also trimmed on the final before and during the round out and flare especially short field landing. It felt like doing slow flight descending on the final and the landing and touchdown were really smooth. (smoothest ever actually)
Nevertheless he did not mention the use of trim on the round out and flare phase, and other instructors either. today I imitate that instructor and use trim enough to maintain Vy pitch during flaring but is that a proper technique??

You trim to maintain any pitch condition you expect to continue for more than, say, 15 or 30 seconds. So, for each speed change, you trim hands off to hold that attitude/speed. On short final you should be trimmed for the appropriate approach speed so that no control force is required. In the landing phase, you forget about trim and just work the pitch to control the landing.
Generally it's a bad practice to roll in more nose up trim to reduce the control forces in the flare. The reason is that if you go-around, you will find yourself at high power, needing to accelerate to best rate of climb, and trimmed for a speed way below that. So the nose comes up, and you have to push hard to maintain the correct speed, frantically retrimming to the proper climb speed. If a distraction happens while this is going on that lets you relax your push, you could slow down and find yourself about to stall.
The urge to do it can be intense in some airplanes: I recall that the Piper Seminole had very high pitch forces (almost needing two hands) in the flare and it was common to roll in an extra shot of nose up trim to reduce the force at the start of the flare.
Same problem though, and potentially even more dangerous in a light piston twin, is if you need to do a go around from the flare after retrimming to help reduce pitch forces, (say a cow walks onto the runway) and an engine quits at that moment, you will really have your hands full. You need to accelerate to blue line, go though the single engine drill, and retrim to control the tendency to pitch up hard.

Probably not relevant for the OP, but there are some aircraft (e.g. B737) where the autopilot trims more nose up than needed (at 1500ft above aerodrome elevation) to reduce required control forces during an autoland.

Yeah that was a workaround to avoid having to upgrade to a more powerful pitch servo. The servo is made to push to hold the slope, which gives it much more range to pull when the time comes.

Is the trim helpful on the final when landing?
Absolutely.  Trimming will lock in a safe approach speed.
No more "high, low, fast, or slow".  Just "high or low".

but remember, the aircraft must remain on the glide path to hold speed.

Once rounding starts, the aircraft is constantly slowing down, requiring more and more increase in angle of attack to remain flying.
This is why they tell you to raise the nose or "flare" as the aircraft settles down to the runway.
One should not be reaching for a trim wheel at this point, when bringing the yoke or stick smoothly back is all that is needed as airspeed bleeds off.
Your instructor may have been showing you that in an emergency trim can be used to control pitch, but finer control can be had by hand feel while eyes are out the window or on the airspeed indicator.


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what are examples of low-frequency navigation receiver in an aircraft?
AIM 5-3-3 a. states when reports should be made to ATC or FSS. and 5-3-3 a. 1-(a) says "any loss in controlled airspace of VOR, TACAN, ADF, or low-frequency navigation receiver capability"
what are example of low-frequency navigation receiver that's in an aircraft? All I found using LF is AM radio, but is AM radio certified to be used in an aircraft?

AM radio is medium frequency (MF). ADF receivers are capable of receiving AM radio stations.

I recently found NDB frequency is from 180-535 kHz, which is LF navigation equipemnt.

The AIM excerpt you cite already lists ADF (which is the receiver for NDB ground stations), the last LF navigation system still in activity. Thus by "low-frequency navigation" AIM might refer to Loran-C, a system shut down between 2010 and 2015.
Before Loran-C, other long range navigation systems have been used: Omega, Decca, Soviet RSDN (Alpha) --perhaps still in use. They are collectively known as hyperbolic navigation systems for they compare the time of arrival (phase) of signals from different synchronized stations, and the locus of solutions for a pair of stations is an hyperbola. The current location is found by intersecting two hyperbolas.
Very low frequency (VLF) and low frequency (LF) waves propagate well on long distances, they are ducted by reflective ionosphere and ground, and can travel across continents and oceans (with areas of silence between hops). This mode of propagation totally disappears for VHF and shorter wavelengths.

Use of the radio spectrum by aviation.


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What is the wiring of 1 plug (.206" or coded PJ-068) aviation headset?
Boeing aircrafts have been using 1 jack headset on commercial airliners in the past. The plug is same as a microphone plug of modern GA dual plugs. Does anyone know how to wire a PJ-068 plug for both microphone and audio?

From what I've gathered, Plantronics MS200 and Telex 5x5 PRO have been using single plug, and looks like single plug PJ-068 connectors still work on modern Boeing two-plug audio panels.


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Sea Level pressure on different charts that has wildly different values
I was an AG in the Navy about 40 years ago and I just picked up a personal weather station.  So not a calibrated barometer at home, I started looking at nearby stations on Weather Underground(WU), https://aviationweather.gov/gfa/#pro advanced map, METARs for close airports, and the NOAA Surface analysis.
I just figured out the observation plots on the aviationweather.  It is the altimeter setting instead of the MB like most station reports.
At some stations, the altimeter converted to MB sometimes is almost 0.7 MB different.  Why?
My next question now is why is WU off from NWS.  Of course, I trust NWS, but it seems like some of their network would have figured out how to get close.

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

First, 0.7 mb isn't a lot.  Using https://www.convertunits.com/from/mb/to/inches%20Hg Going from 1000 to 1000.7 mb changes the result from 29.53 in hg to 29.55... that's like 20' of difference, and probably about the limit of precision for a lot of instruments. When you say "is different", different from what?  What is the truth-source that you're comparing stations against?

Altimeter setting is reported to four significant digits (e.g., 29.92) whereas NWS provides pressure information to five significant digits (e.g., 1018.8). Therefore, essentially the difference you are seeing is roundoff error in the altimeter setting and it's quite small (as was pointed out by @Ralph J in the comments).


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Autopilots: how do they work and how would I implement them
I recently am taking on autopilots, and I dont really know where to start. I want to make a realistic autopilot in my game engine, but I dont know exactly where to start. Is there any sites, documents or videos which start out easily (without all the complex formulas) and then dives deeper into those formulas and why they work?
All I know is an autopilot works with many different systems, and here I come with a bit of advantage. In my game engine, the only forces acting on my plane are the standard lift, drag weight and thrust. Turbulence and all those other obscure, scary things dont exist, so I dont have to worry about the things related to that.
Thanks anyway!

If the physics are simple enough and target realism low autopilot can be implemented by turning OFF some or all of the physics and handing control of speed/heading to the 'autopilot' code and saying it is just really good at it's job of dealing with the physics. Downside of this is odd results entering/leaving autopilot and potentially allowing impossible altitude/speed combinations.

If you don't want to use complex formulas, I suspect that you haven't implemented realistic flight dynamics.
If your flight dynamics are simple enough, you may not need an autopilot at all.  If the user stops inputting anything, the airplane should probably fly straight and level.
Without realistic flight dynamics, why would you need a realistic autopilot?
Common kinds of autopilot are altitude hold, attitude hold, and heading hold.
Altitude hold maintains the current altitude.
Attitude hold maintains the current climb/descent attitude.  You can be in either altitude hold or attitude hold -- but not both at the same time.
Heading hold maintains a compass heading over the ground (say in the presence of winds).
You can probably implement these kinds of modes without any realistic flight dynamics or controls.

Hi there! So for a bit of clarification, I'm trying to remake an airbus MCDU, where you can input a bunch of waypoints, and the computer takes them all in and slowly moves the plane towards them. I needed an autopilot so that the plane doesnt go 90 degrees and pulls back like a fighter jet, but instead turns calmly

I would simply program your 'autopilot' to perform a standard rate turn -- 3 degrees per second, i.e. a 360 in two minutes.  If you look up the equations for a steady turn, you'll find the relationship between turn rate, bank angle, velocity, g's pulled (i.e. lift required) etc.


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Confusion about angle of attack difference between wings in a slip
CFI applicant here. I am experiencing some confusion regarding angle of attack difference between wings in a sideslip. When discussing stability, the PHAK says that that the lowered wing will have a higher angle of attack in a sideslip due to the dihedral. However in a sideslip, if a stall were to occur, the higher wing would stall first and drop. This seems to be contradictory. Any help would be appreciated.

I see dihedral discussed on page 5-18 of the PHAK (FAA-H-8083-25C) but where is the reference to "the higher wing would stall first"?

Depending on the aircraft the fuselage creates significant disturbances to the airflow of the trailing wing. This can reduce the effective area of the wing. The aileron on the trailing wing is also deflected down for the side-slip, which can cause a premature stall on that side. If the trailing and higher wing starts dropping, then it's angle of attack increases even further due to the roll rate and then a full stall on that wing can develop.

Because of the increased sweeping angle of the top wing there is needed for more airspeed velocity for minimum stall speed.The top wing is now a straight wing with the lower minimum stall speed.


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PTERA Aircraft Technical data report
Where can I access data recorded by the Prototype Technology evaluation and research Aircraft or PTERA? I have scoured the NASA technical server but all there is available is details on the project and stability data but none on the aerodynamic efficiency recorded.

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

What makes you think data on aerodynamic efficiency was taken?  The experiment was mostly about stability effects.  Measuring drag in-flight is notoriously challenging.

One of the objectives was validating the aerodynamic efficiency of morphing control surfaces/wings. so, I imagine there would be data recorded on this.


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Air to air private communication
When friends are flying together, how to communicate with each other  through aircraft radio ? Are we allow to use any available frequencies?


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Cabin altitude display on pressurized aircraft; why not display baro corrected cabin altitude?
Pressurized aircraft displays Cabin alt, differential pressure, and cabin climb rate.
It appears to me that the cabin altitude is displayed as non-baro corrected cabin altitude (pressure altitude of the cabin).
My question is what is reason or logic behind choosing to display it as pressure altitude of the cabin as opposed to baro corrected altitude of the cabin?
I'm pretty sure the controller schedules cabin pressure such that cabin pressure is equivalent to baro corrected field elevation upon landing. This would match baro corrected cabin altitude upon landing but based on my experience in my aircraft, the cabin alt display is often several hundred feet different from my PFD's displayed altitude at landing while diff P is zero point zero. If I set my PFD baro to 29.92 after landing, the cabin alt display then matches the PFD's displayed altitude.
Is displaying pressure altitude of the cabin as opposed to baro corrected cabin altitude some industry standard or requirement? Seems non optimal.

I'm not sure what benefit you'd gain from baro corrected altitude. The question we're trying to answer is "can the passengers breathe or not?" which only considers the raw pressure altitude of the cabin.

When the aircraft is above the transition altitude and is flying across the country, with the pilots unconcerned about what the local altimeter setting is miles below them (since they're level at FL whatever), what would be the appropriate setting to give the pressure controller?  Cabin pressurization is all about human physiology, not terrain clearance, and human physiology doesn't care what local pressure is, but rather the atmospheric pressure "here". Or, really, the partial pressure of O2 in the lungs. Which needs no baro correction to know exactly.


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Lift to drag ratio for a given glider
I have data from three wind tunnel tests of a glide bomb at three different pitch angles. For each test, I have graphs showing the drag coefficient, lift coefficient, and pitching moment coefficient as a function of the angle of attack. Additionally, I have the mass, dynamic pressure, and reference area for the configuration. I was asked to determine the lift-to-drag ratio under glide conditions based on the given data. How should I find it?
and why it's not simply the ratio of the coefficients founded in the experiments?

This feels like a homework problem! When you are having trouble with a homework problem, you can ask, but you should make clear that it is a homework

This feels suspiciously like a homework problem -- we generally don't like being asked to do someone's homework.
When you are having trouble with a homework problem, you can ask, but you should make clear that it is a homework, you should tell us what you've tried, and we will try to give you some direction without taking away the learning opportunity of figuring it out for yourself.
In this case, I'll go ahead and answer as if it is not a homework.
Assuming the center of gravity is in a location such that the glide bomb is statically stable, it will glide at a point where the pitching moment is zero.
That will imply a particular angle of attack -- which will correspond to a particular $C_L$ and $C_D$ -- and therefore a particular $\frac{L}{D}$.  It will also (given the wing loading of the bomb) correspond to a particular dynamic pressure (equivalent airspeed).
Start by plotting $C_M$ vs. $C_L$ ($C_M$ on the vertical, $C_L$ on the horizontal).  This should hopefully be close to a straight line with a negative slope.
Either fit a straight line to those points, or interpolate between the data points to find where the chart crosses $C_M=0$ -- you want to know the $C_L$ value.  This is $C_L^*$ -- your cruising CL.
Next. plot $C_D$ vs. $C_L$ (Normally we would plot $C_L$ vs. $C_D$).  Fit a parabola to the data $C_D=f(C_L)$.  If you are doing this by hand, you will need to solve for the coefficients that match the data $C_D(C_L)=a C_L^2+b C_L + c$ -- you have three data points, so you can do it.  (Here I am writing $C_D$ as a function of $C_L$, $C_D(C_L)$).
Once you have that parabola, we will treat it as a drag polar.  Evaluate the drag coefficient at $C_L^*$ -- this is your cruising drag coefficient.
Then divide $\frac{C_L^*}{C_D(C_L^*)}$ -- that is your cruise L/D (again, in the denominator $C_D$ is a function of $C_L$.)
If you have the wing area and weight (or the wing loading), then you can solve for the speed.  Remember
$C_L=\frac{W}{q S}$
and
$q=\frac{1}{2}\rho V^2$
or
$q=\frac{1}{2}\rho_0 V_e^2$
Ignore the dynamic pressure of the wind tunnel (assuming the data has been presented in coefficient form).  The whole point of using coefficients is that you can re-use the data at a different dynamic pressure later.
You can do all of this by hand (including the plotting) or with Excel or any other appropriate computer program.  If you are doing it by hand, you may be tempted to skip the steps where I say to plot the data. Don't -- go ahead and take the time to draw a plot with the data, it will help the whole process make sense in your head.

Hi Rob, I converted the math to MathJax typesetting. Can you do a quick check to make sure I didn't make any mistakes in the conversion?

Thank you. Actually, I encountered this problem during a job interview. I'm new to this field and platform, so I hope it’s okay to ask – and please excuse my likely basic questions. Could you clarify why the solution didn’t consider the gliding angle? Also, when you mentioned calculating the cruising CL, did you mean for gliding conditions?

"Please do my job interview for me" is honestly even worse than "please do my homework for me". The whole point of the exercise is to see what you can do, not what the internet can do for you.

@DarthPseudonym If he knew the interview question ahead of time, I would agree.  However, since it seems the interview is over, I appreciate someone trying to learn from the experience.

If you run through the math and the free body diagram, instead of $L=W$, you get $L=W cos(\theta)$.  When you carry through to $L/D$, you get a sine over cosine that turns into a tangent and cancels out -- so $L/D$ is the glide slope without approximation.  However, when I suggested you use $C_L=W/(q,S)$ to get to airspeed, there is a small angle approximation embedded there which could be resolved with a little more work.


text:
Certifications/diplomas/licenses required for a freight forwarder to contract directly with airlines/shipping lines for independent freight booking
I’m a freight forwarder looking to expand my operations to book air and ocean freight directly with airlines and shipping lines. I’d like to understand the specific certifications, diplomas, or licenses that are generally required to sign contracts with these carriers and operate as their direct customer.
For example, I know that IATA accreditation is essential for working with airlines, and FMC licensing is necessary for NVOCC operations in the U.S. However, I’m unsure if additional certifications are needed for other regions or specific requirements related to handling different types of cargo (e.g., dangerous goods).
Could someone provide guidance on the mandatory and recommended qualifications for both air and ocean freight? I’m especially interested in any requirements for:

Direct contracting with airlines and shipping lines
Issuing House Bills of Lading
Cargo loading and security standards

Thanks in advance for any advice or insights on establishing these credentials to operate independently!

Welcome to Aviation.SE.  Unfortunately, this question is beyond the scope of what is discussed and considered as "on topic" here.

@mins I'm willing to go with whatever the community decides.


text:
Treadmill Problem: Considering the design of the plane
My coworker and I were discussing the treadmill problem from this old post1. I understand that the plane could theoretically fly given that the thrust is generated by the airflow.
Is this true for all types of planes?
My coworker thinks the jet engine with an engine underneath the wings will not fly. He argues that the engine will only create an airflow underneath the wings, not above the wings. I am inclined to agree, but I am not convinced. I can see the airflow generated by the turbines affecting the airflow around the entire plane as well.
I was looking for an airflow diagram of a stationary jet with the engines on. I have not been able to one.
I would appreciate an answer and a reason to why, or why not, the design matters.

"My coworker thinks the jet engine with an engine underneath the wings will not fly. " Have you or your coworker ever looked at an airliner?

The engines do not generate the flow around the airplane.  They grab air in front and throw it to the back.  By doing so, they generate thrust.  Thrust causes acceleration, enough acceleration and you achieve some velocity through the air.  Once at some velocity through the air, the overall shape of the aircraft causes the flowfield that causes lift.

@RobMcDonald Since in this hypothetical question, the plane will be stationary relative to the ground, it will not have velocity through the air? Or the fact that is has thrust, it can have velocity through the air, even if its stationary relative to the ground?

@WPNSGuy Yes. To be more specific, the turbines are in front of the wings at a lower height than the wings. Does this change the fact whether the plane can fly or not on a treadmill?

@trying2understand - the engines, no matter where they are, have a singular purpose. To push stuff out the back, in order to move the whole aircraft forward. This "moving forward" creates airflow over the wings. Which is what allows the aircraft to leave the ground and fly. A "treadmill" has nothing to do with it.

@trying2understand The aircraft will start with zero velocity relative to the ground -- and the wheels are spinning because of the treadmill.  The thrust of the engines will accelerate the aircraft relative to the ground (and the air).  The wheels will have to spin even faster.  When the aircraft reaches an airspeed fast enough to fly, it will be able to do so.  The treadmill just causes higher wheel speed.  Airplane wheels are like a shopping cart -- they just spin, they do not drive anything.

if the treadmill is moving in take off direction and fast enough compared to the air, the plane could brake and be able to take off (for a short time) - basically similar to a glider being pulled by a motorplane or winch. But after starting to fly and losing contact with the treadmill, velocity would decrease (air friction) and consequently it would lose lift and land. If running backwards, the treadmill would increase friction (wheels) and increase the time for the plane to reach rotation velocity (or even hinder it from being reached) -- always ignoring air being moved by the treadmill

@DeltaLima: if you reopen this question (or even better, if you reopen the question in the link) I'd be glad to give an answer to this treadmill problem

The simple and correct solution to the treadmill problem holds true for all aircraft, except those propelled by wheels. No known aircraft is propelled by wheels; unlike a car, an aircraft's wheels are free-spinning, and are often replaced by skis or floats when those suit the terrain better.
The "treadmill problem" isn't a serious physics paradox. It was invented because a lot more people drive cars than know any law of math or physics.
Still, to try and put another nail in its coffin, consider a world without cars. Apply the treadmill problem to a horse-pulled cart, where the horse is outside the treadmill. Will the treadmill inconvenience the horse? Yes, it will create some extra friction. Will it stop the horse from pulling the cart? No. The horse can, if nothing else, drag the wheels across the treadmill.
Now, if we try to bring this into the real world, it's more complicated. No real treadmill can run infinitely fast. If the treadmill is infinitely fast, it can overheat or blow the tires, damaging the aircraft. If both treadmill is infinitely fast, but the wheels perfectly durable, the treadmill will create an air cushion, which is a much better anti-friction device than wheels.
If both the treadmill and the aircraft are subject to real-world engineering limitations, such a contraption won't stop airliners or jet fighters, but it could affect a homebuilt ultralight that can't take a bit more drag.

For another coffin nail, consider an aircraft without wheels. Skis on snow, or floats on water. Magically, they still leave the surface and fly.

If you’re talking about the hypothetical 747 on a treadmill problem, go back and consider the fundamental forces acting on the aircraft during this exercise.
For simplicity some assumptions have to be made:

Treadmill is of sufficient length to allow the aircraft to accelerate to Vr, achieve liftoff and accelerate to V2 while at least 35 ft above the departure end of treadmill belt.

While the tyres make perfect contact with the treadmill belt and rotate to match the belt speed, there is no frictional impedance on the forward motion of the aircraft.

The lift vector generated by the wings is assumed to be perpendicular to the treadmill surface.

The thrust vector from the engine acts parallel to the surface of the treadmill belt but acts in the opposite direction of belt movement.

When the pilot advances the engines to full thrust, the thrust force is the only force acting in the horizontal direction.  This will cause the airframe to accelerate forward at a rate proportional to Newton’s First Law REGARDLESS of how fast the treadmill and the wheels turn.
Initially there is some airflow under the wings of the jet due to the fan exhaust and hot exhaust gases from the engine gas generators.  As the jet picks up speed, ram air begins to flow around the wing, just as in a normal takeoff.  With enough forward speed, movement of this ram air around the wings, combined with an increase in angle of attack on the wings due to raising the nose off the treadmill belt, generates enough lift to overcome the force of gravity and lift the airplane off the belt and into the sky.
The mass flow rate of the jet wash alone, nor its interaction with the lower surface of the wing, is not sufficient to generate enough lift to fly.  The airplane MUST be physically moving forward with respect to an independent viewer stationary on the ground and not standing on the treadmill.  The change in momentum of the ram airflow moving around the wings is what causes the airplane to fly.


text:
How much water should there be in Jet fuel for it to be considered as water contaminated fuel?
In order to consider Jet A1 fuel safe to use, it should have no contaminants present. Given that information, water is a very common type of contaminant, but how much water is there supposed to be in the fuel for it to be considered as contaminated.

A little water being fed into a turbine may not be such a bad thing, but freezing in the fuel lines would be.

There are standards to test fuel contamination, applicable to fuel check methods and detection kits (e.g. ATA 103, EI 1530, GOST 10227 for the Russian Federation), but no standard for the limit itself, only accepted values. For free water, the accepted value varies between 15 ppm (military) and 30 ppm (civil aviation).
The limit used by refuellers and operators, 30 ppm, is set by the International air transport association (IATA).
Principle
Water is not miscible with fuel but they can form an emulsion up to saturation at 40 to 80 ppm of water. The warmer the temperature, the higher the ratio of dissolved water that can be present in the emulsion. When the emulsion temperature is lowered, water in excess separates as free water. This also happens when the emulsion is at rest. This free water is a hazard, e.g. it can freeze and it can allow microbiological growth, with a risk of filter blockage and tank and pipe deterioration.

Source.
FAA
FAA just says in AC 20-125 - Water in Aviation Fuels:

Aircraft engines will tolerate a small amount of free water (30 ppm. is usually considered to be the maximum) if it is in a fine, uniformly dispersed state.

IATA
For commercial transport, the criteria is the recommended limit provided by IATA, the international carriers syndicate, in:

IATA Guidance Material for Aviation Turbine Fuels Specifications, Part III ─ Cleanliness and Handling

For Jet A-1 the tolerance is 30 ppm of undissolved (free) water.
ICAO
ICAO position confirms there is no standard (SARP) for commercial aviation:

The Current Regulatory Provisions on Aviation Fuel Safety: There are no SARPs yet on the aviation fuel.
Following an accident met by A330 aircraft of Cathay Pacific Airlines in Hong Kong in 2010, the International Air Transport Association (IATA) had developed a manual on Civil Aviation Jet Fuel Supply which was later on circulated by ICAO as Doc 9977, Manual on Civil Aviation Jet Fuel Supply. However, this publication is not yet associated with any one specific ICAO Annex.

In Doc 9977, Manual on Civil Aviation Jet Fuel Supply ICAO defines fuel contamination referring to IATA criteria:

Fuel contamination. For the purpose of this document, fuel that is cross-contaminated by other products, [...] fails the visual clear and bright check or exceeds the cleanliness limits set out in IATA Guidance Material for Aviation Turbine Fuels Specifications, Part III, Cleanliness and Handling [...]

Fuel Providers

The IATA value considered as the reference is mentioned in fuel specifications from providers, e.g. in this Total Energies article on fuel contamination, when discussing about storage tanks and delivery:

Maximum content of free water tolerated by IATA is 30 ppm at ambient temperature at point of delivery into the aircraft tank.

also by Chevron:

IATA publishes a document entitled Guidance Material for Aviation Turbine Fuels Speciﬁcations. The guidance material contains speciﬁcations for four aviation turbine fuels: three kerosine-type fuels (Jet A, Jet A-1, and TS-1) and one wide-cut fuel (Jet B). Jet A meets the ASTM requirements, Jet A-1 meets the Joint Checklist requirements, TS-1 meets the Russian GOST requirements, and Jet B meets the Canadian CGSB requirements.

A water contamination of 30ppm in jet fuel is considered the threshold for concern. Once the amount of water is above this the fuel is considered unfit for use due to concerns such as the fuel freezing and blockages.
(This is the case for Jet A and Jet A-1 fuels. Other fuels safety thresholds may differ)
Sources:
Code7700.com
Trustedfuel.com

Is that based on a lab test? My post was more from the pilot's perspective, or the mech doing a DI and seeing a slug of water coming out a sampling drain.

From the perspective of the pilot finding water on a pre-flight or mechanic on a DI, kerosene and water separate out similar to water and gasoline. This means that water in the fuel will slosh around the bottom of the tank as kind of blob or slug of water, since the kerosene is lighter.
When fuel is sampled from the low point drains, if you get water in the sampling cup you will keep draining fuel until there is no more water. It's normal to find small amounts of water in the tank because condensation forms on the inside surfaces above the fuel level, especially if the airplane is left outside overnight.
If you get very large amounts of water (you'd be getting only water for several samplings before kerosene starts to appear) you would need to investigate the source (such as a leaking overwing fuel cap (called a "bung") after sitting in the rain).
However, I'm not aware of any go-no-go standard on water volume in a drain sample for deciding to dispatch an aircraft.
A more common problem is ice crystal formation in fuel when temperatures are low and micro droplets of water are present in the fuel. Most transport aircraft use fuel heaters (normally an engine-oil-to-fuel heat exchanger) to warm it up before it enters the fuel control system of the airplane, to deal with low to moderate ice crystals. Heavy crystal formation can block filters.
The usual mitigation is fuel additives that lower the freezing point of water so that microdroplets in the fuel (that haven't settled to the bottom yet) won't crystalize as free floating particles in the fuel.

This seems to contradict the other answers: Up to some low ppm, water can mix with fuel (may be a suspension/emulsion, may be true mixing)

@Peter-ReinstateMonica Some can be suspended as micro drops, but eventually it settles out and migrates to the drains, water having about twice the Sp Gravity.  In any case my post was based on what a pilot draining sumps would have to deal with, and suspended microdrops would not be apparent.  Testing fuel samples for contam is another story. I made some edits to clarify.

deep draining until... looks like a typo for "keep draining", but I don't have the rep to make a 1-char edit.

@PeterCordes  I was going to concoct a story about how "deep draining" is a thing, but just decided to fix it. lol Thanks

In Compression Ignition (Diesel) Engines, water emulsion up to  2 % improved noise, emissions, power (see M Reza Seifi, 'Fuel' magazine, 2016), it's similar to Water Injection in WW II Aircraft Engines, allowing top power increase for a while without risk of heads and pistons melting, but water injection damages engines.
Total in France had patents on how to prepare Water in Diesel fuel emulsions.
This reduces NOx emissions as it reduces flame, combustion temperatures.
Bacteria thrive in the interface of fuel and condensation water in fuel deposits, its metabolism generates corroding acids, a problem for Industrial Microbiologists to solve.
Heating the fuel was implemented long ago in the Iskra training Jet, was also proposed by an Spanish Utility Model for car engines; if heating fuel is an alternative to carburetor heating to avoid carburetor icing, I don't know.
Blessings +


text:
No Data in FAA Methodology Document but Data in Their Emission Calculator
I hope this message finds you well.
While researching carbon emissions for flights from Los Angeles International Airport (LAX) to Tocumen International Airport (PTY), I encountered an interesting discrepancy. Using the FAA's Emission Calculator, I found specific emissions data for the Boeing 737 MAX 9 pax (IATA code: 7M9). However, when consulting the FAA's methodology document for calculating emissions, I noticed that no fuel consumption or related data for this aircraft model is included.
This raises the question: why would the emissions calculator provide data for the Boeing 737 MAX 9 pax while the corresponding methodology document lacks this information? Could it be an oversight, or is there an alternative explanation?
I’m reaching out to this community to seek insights or guidance on this issue. Understanding this inconsistency is crucial for ensuring accurate carbon emissions calculations in my work.
Thank you for your time and input.

Can you link to the calculator you are using?

Thank you for your response! Could you clarify which specific links you’re referring to? Are you asking for the link to the FAA Emission Calculator or the FAA Methodology Document, or both? I’ll be happy to provide them for further context.

It would be good to provide both.


text:
The "A"s mnemonic for instrument approaches
I used the 6 As mnemonic when I got my instrument rating. I remember them as

ATIS
Altimeter
Avionics
Approach Briefing
Airplane (approach checklist)
Align (DG, ADI)

Similarly to the 5 Ts, having mantras or mnemonics was a helpful way to stay productive even when task-saturated. But while I can find a lot of sources for the canonical 5 Ts, the only thing I see for the As is this article. Respectfully, I think a key feature of the As as I learned them is that you set the avionics up first, then use the approach briefing as a cross-check, so I don't like that presentation as much.
Can anyone point me to resources that list the 6 As as I remember them or a similar mnemonic? I've gotten back to flight instructing after years away, and I'd prefer to share a better resource than "My instructor told me to write this down." I did my instrument rating at Embry-Riddle in 2000, so it could have been something formal there, or just something my instructor heard from his instructor, and so on.
Thanks!

OT, but there is an easy way to memorize morse code, which can be useful for identifying navaids without having to gawk at the little box with dots and dashes. You create a list of phrases with a cadence that matches the letter. Ex: F=Funny Handle: ..-.  B=Brown Chocolate: -... C=Charlie Charlie: -.-. D= Dag nabbit! : _..  E= EH?: . G=Good good boy": _ _ .   I was able to recall those from memory and I haven't thought of them for many years.

when I was preparing for my instrument checkride, I found that mnemonic in a video from Jason Miller's "finer points" youtube channel (although it was only 5 As, it was missing the 'allign')


text:
Is ATIS information - including identifier - available on the internet?
According to Section 2-9-1-a of the FAA's Air Traffic Organization Policy, a phonetic letter is assigned to each tower-issued ATIS update.
This information is available on the ATIS VHF frequency for an airport, or via a phone call to a designated ATIS number for the airport.
There is a passing reference on the Wikipedia page to ATIS being available electronically via a service named "D-ATIS", although I've never heard of this.
I'd love to be able to view this information electronically, rather than having to get my VHF handheld, or the plane's radio going and tune it in before flight. The voice system is frequently engaged. If it was available via the internet, it'd be super-easy to access.
Is there a means accessing the ATIS - including the identifier - for a given airport in electronic form via the internet? If so, how?
NOTE: I know it's possible to get METAR reports, but they are typically automatically generated, not manually adjusted by the tower (as ATIS sometimes is), and don't include the phonetic letter designation issued by the tower and required for initial tower contact.

The short and general answer is: No.
The ATIS is only a VHF recording, but even when recorded digitally, it is not available in a text-base form in many cases which would allow being made public on the internet. In the case of D-ATIS, the information can only be obtained using ACARS, other systems such as CPDLC require special equipment.
With modern technology and communication, some airports have started to use Twitter to broadcast ATIS, however they should not be used for flight purposes, but are only for entertainment.

(Image Source: Twitter - Account: @yssyatis)

What kind of people would read ATIS only for entertainment? ... Ah, don't answer that. :)

Given that this is from AirServices Australia, I'm surprised that there's not a fee charged to access this.

I don't believe that Twitter account is anything official from the airport. I think someone has just created an automatic update system using the Airservices Australia data (see my answer for more information on that).

In Australia the full ATIS and identifier is available on the internet in text form (along with all the weather and NOTAMs) - but it is only available to pilots. The information is provided by Airservices Australia (which is basically our government-owned version of NATS) through their online service called NAIPS. NAIPS is free but to register you need an Aviation Reference Number issued by CASA, which are only available to pilots or engineers or other important people.
To illustrate, here is the ATIS from Sydney (YSSY) from a bit earlier today, they were using identifier K:
ATIS YSSY K   260229
  APCH: EXP INDEPENDENT VISUAL APCH.
        DO NOT PASS THRU, ASSIGNED RWY CL
  RWY: 34L AND R FOR ARRS AND DEPS
  OPR INFO: PARL RWY OPS IN PROGRESS.
            INDEPENDENT DEPS IN PROGRESS
  WIND: 260/12
        XW MAX 12
        DW MAX 3
+ VIS:
+ WX: CAVOK
+ CLD:
  TMP: 27
+ QNH: 1015

How is it "only available to pilots"? Via a subscription service?

I have edited my answer which hopefully answers yours!

yes; thanks. Is this available at all airports where ATIS is used?

Actually it's not, and I'm not completely sure why. I have personally flown into two airports with ATIS - YSBK (Bankstown) and YSCB (Canberra). YSBK ATIS is not available on NAIPS but YSCB is. YSBK is a large general aviation airport but YSCB is mostly RPT passenger planes. Also the YSBK ATIS is recorded by a real person but YSCB is a robot voice. Those must be the reasons why. Also I just checked a few international airports and I can get the TAF and METAR but not ATIS.

@Ben I wonder if the airports that show up are ones that have D-ATIS for planes with that capability? I'd expect Sidney & Canberra to have that capability because they have major/international airline traffic, but it looks like Bankstown doesn't have that sort of airline service so it probably wouldn't have D-ATIS equipment...

In the US ATIS information isn't available on the internet. The tapes (or an equivalent written record) are retained like any other ATC communication though (3-4-2 item "k") and are available via FOIA requests if you have a pressing need for them.
If all you're interested in is the weather most airports that are large enough to warrant an ATIS broadcast are also large enough to have a weather station reporting METARs, which means you can use one of the many available METAR archive search websites (or if you prefer you can dig around on the NOAA website - I used to know the URL for the archive but it's apparently been moved).

Yes, I mentioned that I know I can get METAR information online, but I'm looking for a combined way of getting weather and the designator letter to report to ATC before initial contact.

@CJBS The only way to get the ATIS identifier (for any kind of timely purpose like use in flight) is over the radio. The ATIS identifier doesn't always have a logical correspondence to METAR data. For example if an airport is closed due to an incident they may update the ATIS, but may not generate a METAR or SPECI weather report because the weather wouldn't have changed. (There are services which offer transcriptions of the D-ATIS data, but none I'm aware of are free & D-ATIS doesn't cover every airport with voice ATIS.)

@voretaq7 There are exceptions to every rule: EDLW 260620Z 23004KT 9000 BKN013 04/02 Q1008 RMK ATIS E

@SentryRaven Yes, if the tower enters the ATIS letter in the automated observation remarks that would helpfully provide it to anyone reviewing the METAR :) (It would be really nice if towers did this in the US for those of us with ADS-B receivers - a poor pilot's D-ATIS - but I don't think I've ever seen a US METAR with the ATIS identifier tacked on to the end :-/)

I dont know of a site that has it for every airport but this site has lots of live streaming ATC. It seems they have ATIS for some airports (I found it for JFK) but chances are they will only have it for the big airports however depending on where you fly out of you may get lucky. Again this is the actual audio feed so you will still need to listen to it.

I've known about the LiveATC, but you're right that there's at least one airport's ATIS stream available - and via the internet.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
GA Headsets - is there a standard for the replaceable microphone?
I've noticed that on many (but not all) different types of GA headset, the microphone seems to be somewhat modular, with two holes at the end for the microphone boom to insert into, and two screws at the front that seem to be able to be used to both hold it in place on the boom, and also fasten the two parts of the plastic microphone assembly in place.

Example microphone modules:

Is there some standard for microphone modules, or is what I'm noticing just coincidence?
Background: One of my headset microphones no longer works due to being ... unintentionally regurgitated upon - I'm wondering whether I can just buy one that looks similar.

It's not a coincidence, the connection is a modular microphone standard called U-172/U. The pins it connects to are the U-173/U standard.
You can't just get any microphone that has that connector though, it's not aviation specific. You need to get a microphone which has the right impedance and is designed to work with the voltage on an aircraft communication system. There's plenty of options, some which give better noise cancelling properties than others.
All you need to do is get the parameters of your hurl-covered one and get one with the same parameters.
There's information on aviation connectors and standards here, and here.

Do you have a reference (link) to the standard? I couldn't find anything but links for purchase.

I'm not sure what kind of standard you want but you can get measurements for all sorts of audio connectors on the mouser electronics site. http://www.mouser.com/ds/2/18/Nexus_Catalog-537765.pdf. See my edit for more.

Standard in the sense of the specification as defined by its creators (or maintainers), such as IPsec is defined here https://tools.ietf.org/html/rfc4309 by IETF... Those docs are good, though. Thanks.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Why would a C-17 Globemaster be painted in Qatar Airways livery?
Just seen a C17 Globemaster painted in civilian Qatar Airlines livery.

Any idea for the reason? Is this aircraft for civilian or a military use?

The picture is taken from the web but the plane I saw is actually that one as I live very close to the runway.

Recent news where the c17 may come in handy http://presstv.com/Detail/2017/07/09/527905/Qatar-to-fly-4000-cows-to-address-its-milk-demand

It is a military C-17 of the Qatar Air Force, one of the four in operation.
It is in this livery as it is being operated by the Qatar Amiri Flight, a VIP airline owned and operated by the government of Qatar. The vast majority of the Qatar Amiri Flight fleet is painted in the standard livery of Qatar Airways, like this A340 below.

The aircraft is only operated by the Qatar Amiri Flight, not owned by it. The picture below shows the Qatar Air Force roundel on the underside of the wing.

Source: www.youtube.com

So what does a vip airline use a C-17 for? Seems an odd choice to fly the royal family around in.

It's a bit awkward trying to fit a royal limousine into the cargo bay of an A340.

The US does the same: Air Force One arrives with the president, and in the background a USAF C-5 has already unloaded the presidential motorcade.

Jeez, what a waste of gas.  Can't the prez ride inside in the car while the car rides inside the C-5?

@quietflyer maybe something to do with FAA limits on passengers on cargo aircraft ;)

It is for military use. As you can see from your photo, the registration code is "MAB" and this site links that aircraft to the Qatar Emiri Air Force:

Current fleet:

A7-MAA
A7-MAB
A7-MAC
A7-MAE

Interesting find! The livery makes it appear as if it is intended less for military use than for promoting the national airline. This is a quite expensive flying billboard.

@PeterKämpf I cannot find any data on the livery. Could be used for double purpose: military transport AND civil billboard.


text:
Is there a valid case to do the imposible turn(180)?
It has been said many times not to do the imposible turn(180) after takeoff since almost always it  ends in a fatal crash.
My question is, if you are flying a Cesnna 172, or any single for that matter, and you lose the engine right after takeoff but in front of you there is a high density city(houses, cars, power lines, trees, people walking, etc), should you still avoid the imposible turn or this would be a valid case to do the imposible turn?
Or is there some other case where the impossible turn would be valid?

For several months in 2023, Charlie Precourt's column in EAA's magazine "Sport Avation" exhaustively covered when to 180 back to the runway, for a range of airplanes.

can you briefly mention any of those?

I'll let another EAA member summarize those columns into an answer.  The summary of summaries:  simulate the 180-to-touchdown at safe altitude, including 8 seconds of startled inactivity between power loss and maneuver start.  Afterwards, from your GPS track measure how much height you lost and ground you covered.  Remeasure with max weight, CG at limits, different winds, etc.  Record those numbers for reference.

Doesn't matter if what's ahead of you looks grim.  If you don't have the energy for the impossible turn, you're writing checks your energy can't cash. Since this is already poor energy awareness, it's likely more will follow with asking the wings to do what they cannot and stalling it.

You can't do it, by definition, since it is impossible.  You can try it...

AOPA did a great video on this. The results heavily depended on the specific aircraft. https://www.youtube.com/watch?v=dFVFKq3QqXo

Generally crashing into inhospitable terrain while under control is preferable to a vertical spin into the ground short of flat terrain, which guarantees a bad result.
In any case, it usually isn't necessary to turn around back to the runway, which requires more than a 180⁰ turn since the maneuver is more of a question mark pattern. It's a matter of maneuvering to a survivable surface. "Land straight ahead" no matter what is just as foolish, if landing straight ahead takes you into an oil refinery, as trying to return to the runway from 300 ft. As the old saying goes, the rules and conventions aren't a suicide pact. It comes down to some judgement on maneuvering room from the point of failure.
It's better to forget about the concept of the "impossible turn, yes/no" and think in terms of "how much maneuvering margin does this altitude give me". To make that kind of judgement instantly, it means you need to know your airplane and its gliding ability and your own skill level. An airplane with a good L/D has way more options that a draggy biplane. Taken to an extreme, a 40:1 sailplane can have a tow line break at 300-400 ft and fly a complete pattern/circuit to land at the original starting point.
In general an airplane like a 172, with an L/D of around 9, will need more than 400ft to be able to turn and maneuver all the way back to the runway, if flown expertly and optimally. Go to a safe altitude and try it, and practice it and see for yourself.
But who says you need to reverse direction? There may be a golf course or a highway 90⁰ off the course that can be reached from 200-300 ft.
These eventualities should be part of the pre-flight planning from a particular airport. You brief yourself: If the engine quits at point X at 300 ft, where can I go? Make a few "advance decisions" so if it actually happens, you just react and put it down under control, even if it's trees (even there; if there are tall deciduous trees and a patch of short conifers, put it into the conifers, which will absorb energy like a big hair brush) .
This is part of the normal pre-takeoff checks in gliding, knowns as "Options" at the end of the pre-takeoff CISTERSC Nemonic. You observe the winds, review the terrain, and decide in advance what to do if a rope breaks at less than 400 ft.
I just had a fun and enlightening experience in my towplane checkout recently. We were doing circuits in the tug (a Citabria) and, mindful of some recent turn-back crashes, my check pilot eased the power back somewhere between 300-400 ft, catching me by surprise. After the quick run-through checking switches, carb heat etc, and pitching to maintain speed, I looked down, then back toward the airport, and instantly realized there was no way I could make it back. I pointed to a field about 45 deg off to the left and said "I'm putting it down there". He said "Good boy! Power's yours again".

These eventualities should be part of the pre-flight planning from a particular airport I would imagine this is a critcal part of being a pilot right!!  Great explanation

TY. To the extent you can know the terrain beyond the airport. So much easier these days with Google Earth. It's actually kind of shocking that something very basic to glider training is rarely done with power.

For the sake of simplicity let's assume that the impossible turn in this case is in fact fully impossible, so no borderline cases are considered. The actual choice in this case would be "where do I crash" and certainly there are circumstances where you  preferably crash at the airport, such as the said airport being embedded in extremely densely populated area being one.
I used to fly from an airfield that can be considered as of the aforementioned type. However altruistic it may seem to prepare to crash away from populated areas, the take off briefing was always "in case of engine problems fly straight ahead and find a place to land", while knowing very well there were next to none.
So, is the impossible turn ever a valid choice, yes, but applicable in real life, perhaps not so much.


text:
Is TSA Pre check a security risk?
As we have seen through history, many times, despicable acts of terror and violence have been committed by just "normal" unsuspecting people, that for whatever reason (hate, outburst of anger, mental sickness, etc) something switches in their mind and they commit these acts without anybody expecting it(they were a lovely couple, he was a quiet kid, he looked like a normal neighbor, etc)
This brings me to the point, when a passenger gets to the airport why would you allow one group to go trough a less meticulous screening (TSA Pre) if they could be carrying something harmful.
And if the TSA Pre group is still screened to some extent then why not use the same process for everybody else?
A person that was totally peaceful yesterday, today could want to do harm.

To an evil smuggler, airport security screening is just an inconvenience.  To a terrorist, a security checkpoint is a convenient target.  The TSA's purpose is to please the voters of the legislators who created the TSA.

That is right, I remember what happened at Brussels airport in 2016, they didn't even had to go trough security, they did their thing right there. That's why I don't like agglutination of people, its the perfect target for terrorists.

The idea that somehow a "normal" person "just suddenly flips" and commits a terrorist act is almost never true. Most terrorist acts are planned.

When you say the "same process," are you proposing greater screening for all, or less screening for TSA Pre-check passengers?

@MichaelHall less screening. But what I'm trying to say is that whatever process it is, it should be the same for everybody. ultimately I think TSA should make efficient/faster the normal process instead of creating another different process for a different group as if they were not also humans with the faculty to commit evil.

OK, but do you not agree that some people are less risk than others?  I mean, I agree that all people are equal in the eyes of the law, God, etc. but there is no denying that some elements of society are more bent on crime and mayhem than others.  To deny that fact is actually rather naive.  The current process is aligned with reality more so than what you would propose, and provides benefits to low risk frequent travelers who are willing to subject themselves to heightened scrutiny.

@MichaelHall People are definitely different risk. Some people are 100% risk, others 0%, and almost no one's in between. The relevant question is whether TSA Pre-check is only passable by the 0% risk people.

@Therac - No one is "zero risk". Even those pre cleared by TSA. Just "less risk".

@WPNSGuy I am zero risk: I've never taken to the air with the intent to commit an act of terror, not will I ever.

@Therac - Prove it. Prove it to the security guy standing between you and the aircraft. That is what the precheck is for.

@WPNSGuy Exactly. I know I'm zero risk, but the guard doesn't. The purpose of all checks is to learn this. So the question is whether TSA Pre obtains the right information to filter out the 1-in-billions terrorist.

@Therac - And the "pre check" is to do just that...check and approve you before the line at the airport. Allowing you to skip some of the stuff at the line. Is it perfect? Of course not. So...propose something different.

@WPNSGuy I'm not campaigning - just commenting on the question.

@MichaelHall definitely yes if we look at the numbers you are right, however doesn't mean it can't happen. Even the pilot himself can be suicidal(remember the 2015 GermanWings suicide pilot that killed everybody after the copilot went to the restrooms), which created the procedure to always have 2 persons in the cockpit. My point is, in that same way, that we should all be playing at the same level and not allow someone to have an "advantage" (TSA Pre) over another group of people (Non Pre)

And my point is that everybody should NOT be playing at the same level because not everybody is the same level of risk.

A person that was totally peaceful yesterday, today could want to do harm.

A person who previously went through and passed a security check is less likely to go off today.
Just like needing a security clearance for a job. Not 100% guaranteed to never ever go rogue, but less likely.

I don't buy this answer at all. People with a gripe can build up resentment over time and plan to commit atrocities later, E.G. Killdozer guy, Mandalay Bay guy, etc. Even the 9/11 hijackers had obviously cleared security before in order to get into the US. There's got to be another reason for pre-checks, IMO.

@DannyBeckett The question did not ask for the reason precheck exists.  Precheck exists to collect a fee.  It's also a convenience for frequent fliers who are also frequent donors to political campaigns.


text:
Are carbon fiber parts riveted, screwed or bolted?
For aircrafts made of composite material like carbon fiber, whats the right fastener method to attach the different aircrafts parts?

Generally bonded, bolted or riveted using steel shank with swaged collar type rivets like HI-SHEAR/HI-LITE. You can't use aluminum against carbon due to galvanic incompatibility.
I believe the 787 structure is largely bonded. On the other hand the A-220/C Series, which has carbon wings, uses swaged-collar steel rivets to attach the carbon parts like ribs, spars and skins together as if the wing was aluminum.

... also called "black aluminum" in the trade. Painful to look at when you know composites.

if they are mostly bonded, how do they un-bond when there is need to detach a part(i.e. access area for mechanic inspection)? is it more complicated than a rivet/bolt/screw?

ok so that means the bonding is only done on parts/areas where there is never going to be a need to detach the part(i.e. for inspection)?  In other areas rivets and bolts are used, correct?

@Gabe you figure that out going in, and if you need to detach or get access,  you design for removal using fasteners. Otherwise the bonded assemblies are permanent.

@Gabe With the poor long-term strength of aluminium, certain habits have formed which are rational when you deal with an aluminium structure, but irrational when composites are used. Composites now get punished for the poor experiences we made with aluminium in the past.


text:
Is the procedure to taxi half down the runway to disperse fog still used today?
After the Swissair Flight 306 accident which used the procedure to taxi half down the runway to disperse fog, is this technique still used today?


text:
Are propellers quieter when its drizzling/light rain?
Reading about aircraft noise reduction came across the concept of Micro Jet which apparently injects water into the "tail jet flow field" to reduce noise, so I wonder this concept also translates to open propellers aircraft while in drizzle weather. And if it does, could something like this be installed on open prop aircraft when isn't raining, some sort of mist spray device that can be turned on specially during takeoff and landing(which is the phase where noise reduction is really relevant).

It is my understanding that rain/mist/fog all reduce noise levels in general - is that relevant?

Looking at this paper The Effects of Microjet Injection on an F404 Jet Engine, it seems that there are more parameters than just the presence of water.
They report a noise reduction of max 5dB locally for the following setup:

Pressure (400 psig)
Massflow (in the paper they talk about "8 to 11% of the mass flux of the main jet")
Direction, see the plot below for the influence of the jet angle:

They do not report sensitivities for the variables, but comparing this setup to common drizzle, all factors are very different, so I expect the outcomes to be also very different (likely much less to nothing in the case of drizzle)

This paper sounds like it's discussing a jet engine; the question is about a propeller.

Ah fair point, I saw Microjet and followed the resources leading me to jets.


text:
How can you identify VDP on Prescott ILS 21L without DME?
Prescott ILS 21 L IAP does not note DME required, although it clearly says "Use I-PRC DME on localizer course". If you do not have DME, can you do this approach? or if your aircraft is not equipped with DME, how can you identify VDP?

Note the bottom right says (emphasis mine)

ILS or LOC/DME

Which means that to use the localiser approach a DME must be required, otherwise it would specify LOC only.
So if you have no DME, you can use this approach for ILS, but if not equipped, and you want to do a Localiser approach you need a DME.

I missed that note!

I would add to the other answer that there is no VDP for an ILS (or other approaches with vertical guidance) as these approaches take you all the way down to the DA from which you either complete the landing or go missed from there. VDP only makes sense in a non-precision approach (like the LOC/DME in this case) where you will be close to MDA until presumably the missed approach point (which would be too late to make a normal landing...thus the VDP being necessary). So the graphical depiction of the VDP on the chart is only for the LOC/DME.  The ILS doesn't have one.  This is also demonstrated by the fact that the 2.6 mile DME point that marks the VDP shows an asterisk which denotes it's for the LOC only. That point is meaningless for the ILS.  Hope this helps add color to the other correct answer.

I hadn't even picked up on that, so thanks for pointing it out. A great additional bit of info - I'm still not entirely used to US-style/Jepp charts so I'm also learning how to interpret them.

I’d like to add that both the procedure title and the LOC only note are because this chart is old. If this was a current chart, the title would be ILS or LOC RWY  21L, there would be a DME required note in the pilot briefing bar, and there would not be a LOC only note in the profile.

@timbo, Since this is the most current chart as of this post, I’m guessing you mean that the next time the TERPS folks at the FAA update this procedure they will change the name based on new standards. Is that what you mean? Thanks.

@BillWilliams yes, that is what I mean. The currently published chart does not align with the currently published FAAO 8260.19 or IAC 4 specification.


text:
No FAF on IAP chart other than VOR or NDB?
I know no FAF depicted is common thing for some VOR IAP or NDB IAP. I'm just curious, other than VOR approach or NDB approach, are there any IAPs that does not have FAF in the profile view?

If there is no FAF, the final segment of the approach begins when you are established on the final track after a procedure turn or racetrack.

Note that the terminology for FAF (fix) and FAP (point) differs between ICAO and the FAA. See here for more details.

The only approaches that do not have a FAF would be one that has a procedure turn and no way to identify the FAF.
In ages past, the pilot would navigate to the VOR or NDB which was on the field and commence the approach (IAF) from that point.
As they turned inbound, it was considered passing the FAF.
There shouldn't be any RNAV (GPS) or other apporaches like this anymore.

why there is no way to identify the FAF as it has a procedure turn ( like a teardrop turn or back course?)

PT inbound is considered the FAF.  The navaids available for use on these procedures do not allow a pilot to positively identify a waypoint inbound.  There is most likely no DME available, and no other navaid expect the primary to use to positively identify another point.


text:
What are the 3.7 and 2.7 in the parentheses in this chart?

What are these numbers (3.6 2.7 and 4.9)
Do they indicate distance?

Yes, that is distance in Nautical Miles for the segment indicated with the arrow. Data is depicted for each with minimum altitude, course, and distance.

And the specification that covers this is section 3.4.4.13, Terminal Routes. https://www.faa.gov/air_traffic/flight_info/aeronav/iac/media/IAC4/IAC-4-04SEP2024-complete.pdf#page77


text:
can you refill zippo with Avgas?
is it possible to refuel the zippo with avgas such as 100LL or 100?
I heard gasoline can be replacement of Zippo fuel, and I got curious what about Avgas?

https://en.wikipedia.org/wiki/Tetraethyllead#History
Read that section of this page

"is it possible to refuel the zippo with avgas": possible yes, but is it safe?

What substances one can put in a cigarette lighter is not an aviation question.

people used 97 Octane petrol for zippos as far back as WW2, including soldiers on the front lines. Good for your health? No. Worse than smoking? Probably not. 100 Octane avgas is pretty similar.

Do not in any circumstances use avgas in a lighter, to light charcoal, or for any other use where it or it's fumes may come into contact with humans or animals.
Avgas contains Tetraethyl Lead (TEL) which is toxic in a number of ways, which is why they are trying to phase it out. Don't do this.

+1, you're right, but this is to be put in perspective: Lead is dangerous, but at which concentration in air? and after how much time of exposure? We are talking about a 2 cubic cm of gazoline, not about someone living close to a road in the 60s for a couple of decades. For someone smoking and directly inhaling smoke, TEL is not the main concern, and likely not a concern at all.

TEL can be absorbed through the skin, and through inhalation. Given that someone without understanding the risks may first get it on their skin while filling their lighter, then inhale it when they light their cigarette, and may repeat that many times, I'd say it's a legitimate concern.

@mins 2mL of 100LL contains about 1 milligram of lead as TEL. That's enough to bring the interior of a compact car (for example) to several times the allowed limit for industrial workers who work with the stuff.

@mins Exhaust emissions decline roughly as 1/r^3. With a lighter, you're inhaling most to all of the lead, versus a much smaller amount with reasonable distance.

@Chris: Your example must be adjusted to the smoker context. At a rate of one lighter refilling per month --> divide 2 ml by 30 for a day. Smokers don't fill their 6-liter lungs with gasoline vapor, but maybe with 90% of fresh air --> divide by 10. For the exposure time, say 20*2s=40s a day vs. 8 hours in your worker example, divide by 720. The time x concentration ratio for lighting 20 cigarettes a day with 100LL is only 1/200 000 of the one in your car example (so likely legally allowed). Not claiming a scientific demo, only rough figures for a raw comparison.

@mins The TEL in the lighter is enough to bring the whole car up to several times the limit for the whole day. Using the lighter in close proximity to their face means they're going to be inhaling rather more of it than if it were evenly distributed throughout the air of the car they were in. In 8 hours, you breathe in roughly 2 cubic meters of air- corresponding to about 150 micrograms of TEL at the legal limit. Or 1/7 what's in the lighter. Plausible for a heavy smoker to go through in a day.

he asks if it's possible, not if it's safe :)

also, will it kill you before the smoking does? Probably not.


text:
what is "short range clearance procedure" like?
in my oral exam guid book
it says
"a traffic clearance issued prior to departure will normally authorize flight to　the airport of intended landing. Under certain conditions, at some locations, a short range clearance procedure is used, whereby a clearance is issued to a fix within or just outside of the terminal area, and pilots are advised of the frequency on which they will receive the long range clearance direct from the center controller"
what is the "Short-range clearance procedure"? and what is it like?

I don't know that this is common at all in the usa anymore, but the idea is that you would file a flight plan along the lines of
KABC..XXX.V10.YYY.J20.ZZZ..KDEF

and instead of being a full clearance all the way to "DEF airport" instead you would only be cleared so far as "YYY VOR." That is your clearance limit, and you would expect to receive further clearance before you reach the VOR. If you don't, you hold over the VOR and ask ATC for instructions.
Again, I don't know if that's common at all anymore. Current ATC procedures tell us to clear you all the way to your destination airport (even if it lies within uncontrolled airspace).
Something which might be a little more common is if you plan to fly VFR cross-country but a low layer of IMC prevents a VFR departure. You can request, or even file, IFR to a nearby fix—ideally this will be some fix right before but not all the way to the border of the TRACON or Center sector. ATC will clear you to that fix with the expectation that you'll cancel IFR once you break out on top. (This is sometimes referred to as an "on top" or "climb to on top" clearance, but it's not the same as a a true VFR-on-top clearance.)


text:
How can I identify VDP on VOR 1 runway 36 at KOCF
at Ocala international airport (KOCF), they have VOR runway 36 approach. The VDP is 2.7 NM away from the OCF vortac. But my aircraft is not equipped with DME. How can I identify the VDP without using DME?
(My aircraft is equipped with GPS and Dual VOR)
At first I thought I can use GPS to see the distance but GPS substitute is not allowed on final approach segment…

It does seem strange to have it be a "VOR approach" with "DME required" rather than just calling it a "VOR/DME approach."

“VOR/DME” is no longer the current standard naming convention. If DME is required in the procedure (which it is, for the missed approach), then it should have the note in the pilot briefing bar. This also applies to an ILS or LOC procedure.

A VOR/DME approach indicates that DME is required for the final approach segment (FAS).  If DME is required outside of the FAS (FAF to MAP), a note is applied.

If an approach is VOR/DME approach, can you use GPS to identify waypoint on a final approach segment?

Yes. You cannot use GPS as the only means of lateral navigation on the final approach segment. I recommend you read AC 90-108 or the draft AC 90-119, section 11.4.6.

@wbeard52, that naming convention is outdated. The current naming convention is to simply call it VOR. The equipment requirement box is for any equipment required between the IAF through the missed approach.

@Timbo. Do you have a reference for your statement?  My understanding is the equipment required from the FAF to MAP is listed in the approach title.  i.e VOR/DME.  If there is equipment needed from the IAF through the MAP but not on the final approach segment (FAS), it will be listed with a note on the chart somewhere.

@wbeard52 With the missed approach point being the OCF VOR, you don't seem to need DME until you get to the holding fix.

@RalphJ  I agree with you.  That is why there is a note that DME is required but because DME is not required for the FAS, it is not in the approach title.  A cursory look of the newest terminal procedures (2413) shows two changed procedures with DME still in the title.  Both require DME for the fAS.  https://aeronav.faa.gov/d-tpp/2412/compare_pdf/06239nda_cmp.pdf  https://aeronav.faa.gov/d-tpp/2413/compare_pdf/00367vyty3_cmp.pdf

@RalphJ how do you get to the MAP without using DME? from my understanding I guess you need to measure distance (16NM) on the R355 on OCF VOR by using DME unless you use the suitable rnav (GPS)

@ShinO The MAP, the point at which you must go missed, is the VOR. You need DME or GPS to identify the missed approach holding fix, which is the 16 mile point.

@wbeard52 it was a change to the 8260.19 that happened years ago. https://cfiruss.blogspot.com/2018/05/goodbye-dme-hello-equipment.html?m=1
In the current 8260.19, it is covered in section 8-6-9.

DME is required, and there’s no way to identify VDP without DME.
↑
this is my first thought but actually you can use GPS to execute the missed approach

DME is required for the missed approach. That said, you can still use GPS to identify the VDP. You just can’t use it for final approach lateral guidance.

can you still use GPS to identify missed approach holding point?

yes, absolutely.


text:
How they enter class D airspace at KOPF?
I noticed KOPF (Miami Opa Locka Executive) is class D but surrounded with huge class B of Miami international airport. How does the OPF ATC vector an aircraft without radaring through transponder? or do they have a radar service even though KOPF is class D

Towers don't generally vector aircraft. They may or may not have a radar, but their primary means of providing services are visual and procedural. If they want you in a specific place in their airspace, they will generally give landmarks (e.g. "stay west of the freeway") or traffic pattern instructions (e.g. "enter left downwind runway 1") or something else besides assigning you specific headings.
While in the surrounding class B/C you will generally be talking to an approach controller who does have a radar. Although if you look at the chart carefully you'll see it's actually possible to get to KOPF without entering class B or C airspace.


text:
Is ATL-98 Carvair still alive in the US?
Is ATL-98 still operative or at least displayed within the U.S.?
According to Wikipedia, N89FA is based in Gainesville, Texas, at KGLE, but is it true?
https://en.wikipedia.org/wiki/Aviation_Traders_Carvair

A total of 21 DC-4 were converted to ATL-98. According to articles, the three last flying airframes have been:

N898AT: Destructed in an accident in 2007.

9J-PAA: Not operative. Most recent picture in March 2022. De-registered from Zambian register and many sites add it has been scrapped, supposedly since the picture was taken.

N89FA: Not operative according to CNN, likely correct but to be confirmed. Currently registered by South African Air Lease, with an expiration date in 2028. Most recent picture shot in April 2024.

As of today, no ATL-98 is supposed to fly. N89FA, which registration is valid until 2028, is visible on Google Maps (aerial view dated 2024), but is not visible on Bing Maps (aerial view is not dated precisely).
It's likely possible to get better data, I'm posting this only as a basis to start with.

References
CNN, in 2021:

As of 2021, no Carvair is known to be operative, although a couple of airframes are in long term storage. Their airworthiness status is uncertain.

One of them is in Gainesville, Texas, where it has been parked at the local airport for a number of years.

The other belongs to Phoebus Apollo Aviation, a South African pilot training school, based at Rand airport in the outskirts of Johannesburg.

Mentour Pilot, in 2021:

The last ATL-98 Carvair to fly was written-off after a crash-landing in 2007, in Alaska.

Here’s a picture of N89FA that I took on September 16, 2024 at the Gainesville, Texas airport .

Does it work and fly

Looks in the same condition as in April, deflated tires, peeling rudder paint, and rudder slightly deflected by the same angle.


text:
Do airliners use more fuel at low altitude than high altitude?
Air density at lower altitudes is higher, and thus provides more resistance to objects moving through it. Is this higher density enough to practically impact the fuel efficiency of an aircraft flying at low altitudes?
For example, if a B777 enters a holding pattern for 60 minutes just outside an airport at maybe 5,000', is it going to burn significantly more fuel than if it had (for whatever reason) entered the same holding pattern in the middle of cruising at 40,000'?


text:
What model of aircraft is this?

So, what type of airplane is it?

Where did you get this photo and why is it so oddly cropped?

I don't know. Friend sent it to me.

It's from Tumblr apparently.

I prefer the uncropped image.


text:
Do professional pilots have to show their passports every single time when flying back & forth between the same airports?
What process do pro pilots have to go through with their passports when on the clock?  Are they afforded any shortcuts or do they have to go through security EVERY SINGLE TIME?

They have to go through security, using the flight crew entrance which is separated from passengers. Same applies to flight attendants as well.

Not necessarily for every flight. On short-haul it's not uncommon to fly 2-4 legs per day, and crews don't have to leave the aircraft between the legs. Then again in some countries, for example Russia, border control comes to the aircraft to check the passports even when the crew stays in the aircraft.

Are you asking about immigration controls or the security screening?

@phoog It would be interesting to learn about the immigration part too!

I assumed you were asking about immigration because you asked about passports.  A pilot flying a domestic flight doesn't need a passport at all.

Pilots (and aircrew) usually go through an expedited security screening, usually separate from passengers, in order to reduce wait times.
For example, US TSA has a program called the Known Crewmember Program that allows pilots and crew members to bypass normal (passenger) security line.
Pilots (and aircrew) have to show the documents as required by the local authorities. Usually, this will be the passport/visa or General Deceleration. This varies from country to country.

So, even if the pilot & crew is flying between the exact same two airports all day they have to go through some form of screening?

General Deceleration? Didn't they do that on the runway? :-)

Pilot and author Patrick Smith covers this subject in his online column Ask the Pilot:
"But of all the half-baked measures we’ve grown accustomed to, few are sillier than the policy decreeing that pilots and flight attendants undergo the same x-ray and metal detector screening as passengers...An airline pilot who once flew bombers armed with nuclear weapons is not to be trusted and is marched through the metal detectors. But those who cater the galleys, sling the suitcases, and sweep out the aisles, have for years been able to saunter onto the tarmac unmolested.  If there has been a more ringing, let-me-get-this-straight scenario anywhere in the realm of airport security, I’d like to hear it."

So the answer is "pilots and flight attendants undergo the same x-ray and metal detector screening as passengers"?

Exactly. Pilots are not allowed to carry scissors, bottled water, or penknives aboard. Patrick reports that airport security confiscated his Leatherman toolset just as they have from so many passengers. The TSA does not seem to have tumbled to the fact that the pilot of a large jet airplane is armed with a large jet airplane and does not need nail clippers if he wants to make trouble.


text:
Is there a resource that lists what's outdated in "Stick and Rudder"?
The classic book is awesome but I do know some of the terminology is outdated and perhaps some other things.  Is there a site etc. that keeps track of what's outdated in the book "Stick and Rudder" and what the newest equivalent terms?

I'm not aware of such a list although I would say 99.99% of this book is not outdated.
Maybe some of the terminology is outdated when it talks about the "gaits" of the aeroplane for example which is an horse term apparently.
I wouldn't say anything else is though certainly not the concepts, because the air is the same, the laws of physics are the same and human nature the same as it was 70 years ago. Its a very insightful book that should be every pilots reading.
Maybe it goes on more about tail-wheel aircraft and there are fewer of these aeroplanes around today but this only applies on the ground and is still very interesting even for nose dragger pilots like me.

I would say that it's precisely because tailwheel aircraft are now the "rare plane" on the flight line that those parts of Stick and Rudder are even more relevant today :)

I know the concepts are fine but if there is any old terminology it would be good to know the modern version.

What is "gaits" now called?

By gait I think its a bit of an analogy that means mode of flight. There are eight gaits or modes that an aircraft flies in, with the horse it might be walk trot gallop with an aircraft these are level flight at high angle of attack, normal level flight, dive, normal glide, mushing glide, climb, stall, powered descent I think they were.

@Philip Johnson Nose dragger? Slang for a "regular plane"?

Thats my slang I think... However Stick and Rudder uses the term "Flippers" to refer to the elevators. When you read it, I think its fairly obvious what is old speak, most of it is the same as today,

@verve: But tricycle-geared aircraft don't have noses that sit noticeably lower than their tails (at least not usually; the A330 has a nose that sits slightly lower than its tail on the ground, but that's an exception), while taildraggers do have tails that sit much lower than their noses (hence the name).


text:
Standard Airliner Roll Rates Under Autopilot Control?
Do Boeing-Airbus planes under autopilot control adhere to standardized roll rates during routine maneuvers?
For Example: A 5 degrees per second roll rate between 0 and 20 degrees of bank?

On a 737, the roll rate is greater when rolling from level flight to a 30 degree bank than when rolling to a lesser bank angle.  The bank angle to be used in HDG mode is selectable between 10 and 30 degrees, in 5-degree increments.  In other modes such as LNAV and Localizer, the AFDS decides for itself how much bank it will use, as well as how quickly it will roll into that bank.  Capturing a localizer, for instance, tends to be pretty aggressive if the intercept angle is high; if the angle is shallow, the bank and roll rates tend to be much less.
I have to imagine that this, along with pretty well everything else, is specified somewhere in some Boeing document, but I don't recall ever seeing those numbers published in pilot manuals.